1. Field of the Invention
The invention relates to an image forming apparatus.
2. Description of Related Art
A conventional image forming apparatus such as a printer, a copier, a facsimile, or a multi-function device, for example, a color printer is provided with image forming units (developing units) for respective colors of black, yellow, magenta and cyan. In each image forming unit, the surface of a photoconductive drum is charged by a charging roller, then is exposed to light from an LED head to form an electrostatic latent image. A thin layer of toner formed on a developing roller electrostatically adheres to the electrostatic latent image on the photoconductive drum, so that a toner image is formed thereon. Then, the color toner images on the respective photoconductive drums of the image forming units are sequentially transferred to a sheet by transfer rollers and are thus superimposed on the sheet, so that a color toner image is formed on the sheet. The color toner image is fixed on the sheet by a fixing unit to form a color image thereon. Remaining toner on each photoconductive drum after the transfer is scraped off and removed by a cleaning blade.
In each image forming unit, as the toner on the developing roller adheres to the electrostatic latent image formed on the photoconductive drum, the developing roller is designed to be pressed to the photoconductive drum by predetermined pressure force (see, for example, Japanese Patent Application Laid-Open No. 2005-331567).